Manifestations of leukemia are due to suppression of normal blood cell formation and organ infiltration by leukemic cells. Inhibitory factors produced by leukemic cells and replacement of marrow space may suppress normal hematopoiesis, with ensuing anemia, thrombocytopenia, and granulocytopenia. Organ infiltration results in enlargement of the liver, spleen, and lymph nodes, and occasionally, in kidney and gonadal involvement. Meningeal infiltration results in clinical features associated with increasing intracranial pressure (eg, cranial nerve palsies).

Findings at Diagnosis in the Most Common Leukemias

Feature

Acute Lymphocytic

Acute Myelogenous

Chronic Lymphocytic

Chronic Myelogenous

Peak age of incidence

Childhood

Any age

Middle and old age

Young adulthood

WBC count

High in 50%

Normal or low in 50%

High in 60%

Normal or low in 40%

High in 98%

Normal or low in 2%

High in 100%

Differential WBC count

Many lymphoblasts

Many myeloblasts

Small lymphocytes

Entire myeloid series

Anemia

Severe in >90%

Severe in >90%

Mild in about 50%

Mild in 80%

Platelets

Low in > 80%

Low in > 90%

Low in 20 to 30%

High in 60%

Low in 10%

Lymphadenopathy

Common

Occasional

Common

Infrequent

Splenomegaly

In 60%

In 50%

Usual and moderate

Usual and severe

Other features

Without prophylaxis, CNS commonly involved

CNS rarely involved

Sometimes Auer rods in myeloblasts

Occasionally hemolytic anemia and hypogammaglobulinemia

Low leukocyte alkaline phosphatase level

Philadelphia chromosome–positive in > 90%

Classification

Leukemias were originally termed acute or chronic based on life expectancy but now are classified according to cellular maturity.

Chronic leukemias

Chronic leukemias have more mature cells than do acute leukemias. They usually manifest as abnormal leukocytosis with or without cytopenia in an otherwise asymptomatic person. Findings and management differ significantly between chronic lymphocytic leukemia (CLL—see Chronic Lymphocytic Leukemia (CLL) ) and chronic myelogenous leukemia (CML—see Chronic Myelogenous Leukemia (CML) ).

Myelodysplastic syndromes

Myelodysplastic syndromes (see Myelodysplastic Syndrome ) involve progressive bone marrow failure but with an insufficient proportion of blast cells (< 30%) for making a definite diagnosis of AML; 40 to 60% of cases evolve into AML.

Leukemoid reaction

A leukemoid reaction is marked granulocytic leukocytosis (ie, WBC > 30,000/μL) produced by normal bone marrow in response to systemic infection or cancer. Although not a neoplastic disorder, a leukemoid reaction with a very high WBC count may require testing to distinguish it from CML (see Chronic Myelogenous Leukemia (CML) ).

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